A few things I've noticed:
1. A lot of conversations happen before that many people are interested. Subreddits tend to attract mavens, and they often discuss things months or years before people really care (or the marketing team for whatever is being discussed is even looped in). Pay attention to when the posts you're looking at occurred. In a lot of cases, they were there earlier than you'd expect.
2. There is incredible dispersion in where conversations on a topic occur. It's not uncommon to have 10s or 100s of different communities discussing the same thing, and its not clear which is going to end up being the place people trust. Many of the sub-communities are also somewhat mutually exclusive(geography, android vs ios, etc), meaning it's going to look incredibly insincere if the same account is posting in a bunch of them.
3. Reddit posts allow negative feedback in a way few other venues due, especially not pages optimized for SEO and controlled by a single entity.
4. It is one of the few platforms with an appetite for long-form content. It is almost an anti-Twitter. Meaningfully moving a Reddit discussion on a single popular post could take hours if it could be done at all. For communities with more lasting artifacts like a wiki, it could be practically impossible.
5. As others have pointed out, the subreddits aren't controlled by and don't have the same incentives as Reddit Inc. Optimization tools aren't going to generalize well since what it takes to get to the top of each is different.